In an optical coherence tomography (OCT) apparatus (hereinafter abbreviated as an OCT apparatus) of the related art using a tunable light source, an object is irradiated with light, the wavelength of the irradiation light is continuously changed, and reference light is caused to interfere with reflected light components returning from portions of the object having different depths. By analyzing frequency components included in a temporal waveform of intensity of interference light (hereinafter abbreviated as an interference spectrum), a tomographic image of the object is obtained. The frequency components are analyzed by subjecting the interference spectrum to Fourier transform processing. To obtain a tomographic image that has little distortion and noise, it is necessary to sample the interference spectrum at equal wavenumber intervals and to subject to the interference spectrum to Fourier transform processing.
In the related art, to sample the interference spectrum at equal wavenumber intervals, the timing of wavenumber selection is determined by separating part of the irradiation light and monitoring the part with a detector via an interferometer such as an etalon. In this way, a system for determining the timing of wavenumber selection (a k-trigger generating unit) and a system for detecting the intensity of interference light (a measuring system) are separately provided, and sampling is performed by synchronizing the systems. More specifically, the k-trigger generating unit inputs k-trigger signals (sampling triggers) to the measuring system at equal wavenumber intervals, whereby the interference spectrum is sampled at equal wavenumber intervals (see PTL 1).